Linux Recovery with Live USB and Chroot¶
Today, my Linux system crashed unexpectedly.
My dual-boot system has a habit of imploding when Windows updates it’s boot config. When my graphic adapter and wifi stop working, I am left with a mostly inoperable system.
Rather than reinstall Ubuntu all over and wreck all my configuration, I prefer to attempt a recovery using a live USB.
The system can’t start because we needed to update the boot partition, but we didn’t get the updates done before something crashed the system (or the OS refused to boot). Or something else is terribly wrong.
Whatever the cause, a lot of the times a apt upgrade or dnf update
is all a system needs, but there is no easy way to get there with a dorked
boot partition.
Tutorial¶
Live USB¶
You’ll need to find a 4GB USB drive (Hopefully USB 3.0).
When repairing my dual-boot, I’ll use my operable Windows installation to prepare a live boot USB if I don’t have one on hand.
When making a bootable Linux USB on Windows, the tool to use is Rufus.
Tutorial on making a live USB on Windows with Rufus from Canonical:
Boot from USB to the Live system¶
How to do this step varies for each computer. Usually mashing f12 works on Dell computers.
Select “Try or Install” when GRUB asks you what you want to do next.
Another pop up in the GUI will probably ask you this question again. Select “Try” to start the live environment. If you have a live distro that is only CLI, that’s fine too!
What you are looking for here is a way to get to a shell prompt with working drivers.
Prepare to Chroot¶
Our goal is to hand the reigns of our functioning system to the root of the filesystem that we are struggling to boot.
The Archlinux Wiki has a great article about using chroot:
Begin with making directories to mount your chroot environment onto:
$ sudo -i
# mkdir /rescue
# cd /rescue
To start, let’s find our root (/) filesystem. This system is likely to be fine, but we can’t boot far enough to utilize it to it’s full potential.
Try ls /dev and fdisk to find the root to your linux system. Mine is
a ext4 filesystem that lives on /dev/sdb4.
To mount the / onto our chroot environment:
# mount /dev/sdb4 /rescue/
Next, we need to figure out where the dorked boot partition lives. Since we
are on a live system, our current /boot isn’t what we want our chroot to
effect.
I use a combination of ls /dev and fdisk to identify the dorked partition.
Let’s hand our dorked /boot to the a mountpoint at /rescue/boot/
# mkdir /rescue/boot
# mount /dev/sda3 /rescue/boot/
Next, we want to hand over access to proc and sys this passes through PIDs
and system device settings:
# mkdir /rescue/{proc,sys}
# mount -t proc /proc proc/
# mount -t sysfs /sys sys/
Now, we bind mount /dev and /run:
# mkdir /rescue/{dev,run}
# mount -o bind/dev dev/
# mount -o bind/run run/
If you are doing this on an EFI boot system, you’ll want to bind mount your EFI variables. This important for fixing boot related issues on EFI.
# mount -o bind /sys/firmware/efi/efivars sys/firmware/efi/efivars/
Chroot into /rescue¶
Finally, the moment of truth. chroot into /rescue:
# chroot /rescue
If your prompt just changed, you’ve done something right! I am dropped
into a bash shell as root, and when I ls /home I see that I
am where I belong.
Anything we do in this sub-shell will act upon our dorked /boot and root
directory.
Hope this fixes it!¶
Cross our fingers, and run:
# apt update && apt upgrade -y
For good measure, double down on building initramfs:
# depmod -a
# update-initramfs -u
Exit chroot¶
Type exit to leave the chroot environment.
Unmount directories¶
cd to home, and unmount all those /rescue directories:
# umount --recursive /rescue
Reboot¶
# shutdown -r now
Alternatives¶
If you managed to update the chroot enironment, but your system still doesn’t boot, you have the tools you need to recover files from your broken system before reinstalling your Linux distribution.
Boot into the Live environment
Stash whatever you need from the old root filesystem
Blow all of the problems away with a fresh system install.
I usually consider distro hopping when this happens, but I prefer Ubuntu for a dual-boot with Windows because its installer makes safely installing Ubuntu simple.